There is no way to directly create customer cards in the Shopware Admin. However, you can create customer cards yourself using any EAN code generator from the internet and the customer number.
It's important that you select Code-128 as the format for the EAN code and prefix the customer number with ^8. For the customer number 10059, you would therefore need to enter ^810059 in the EAN code generator. You can then scan the barcode created this way at the till. Thanks to the prefix, POS automatically recognizes that this is a customer and selects the corresponding customer account.